I'm running RAID 1 on an Adaptec 6405. I'm trying to decide if I need to install the ZMCP on the card to provide Cache protection. Adaptec's ZMCP is the equivalent of a BBU - battery backup for the cache.
I've enabled write caching in the controller bios to ensure the system performs well.
I can understand cache protection being required for stripping. But is it required for mirroring?
Is the risk of running RAID 1 without cache protection (a BBU or Adaptec's ZMCP) any greater than running a machine with a normal SATA controller?
If anyone has a Adaptec 6405 with the AFM 600 daughter board would you be able to tell me if the AFM 600 protudes off the side of the card, and if so by how much?
The motherboard only has one PCI Gen2 slot that the Adaptec 6405 card fits in and in this slot the side on which the ZMCP goes is only a centimeter or so from the side of the case.
Answer
Cache protection is about protecting what is in the controller cache "before" it is written to the disks. So if you have write cache enabled on an array, then the data is written into the DDR memory on the controller ... then written do the disk (when the disks are not so busy). This principles remains no matter what RAID level is used. So if you want to protect the data that the OS has written to the disks, but the controller has not yet physically written to the disks, then you need cache protection. BTW: running any spinning disks without write cache is as slow as a wet week. N
No comments:
Post a Comment